Valdemar Poulsen, Danish electrical engineer, c 1920s.
© Science Museum / Science & Society Picture Library
Etching of Vlademar Poulsen (1869-1942). Poulsen was born in Copenhagen, Denmark and worked for the Copenhagen Telephone Company. In 1898 he invented the Telegraphone; the first wire recording device and a forerunner of the magnetic tape recorder. Poulsen found that by pasing an electromagnet over a wire as he spoke into a connected microphone, the wire would become magnetised thus recording the sounds he made. He also worked to improve wireles transmision and in 1903, together with Peder Oluf Pedersen (1874-1941), developed the Poulsen arc generator, which was capable of transmitting continuous radio waves and enabled speech to be generated up to a radius of 150 miles. Published by the International Telecommunication Union. Dimensions: 230mm x 190mm.